Certainly, the passengers are symbolic of society, but I believe it is more specific than that. They are anonymous, basically faceless. They are certainly not presented as individuals. They get on and off the train, but really make no progress. This could symbolize the lack of progress America was making in race relations.

Baraka's play is very much a protest against against the cycle of white domination, and the passengers are a big part of that. They are oblivious to the game that Lula is playing with Clay, stubbornly staying more focused on their own small world. They can't see what is happening right in front of them; this symbolizes the community (white and black) that is not outraged about the racism that is all around them. This was the audience that Baraka was trying to reach.